Multiway connection for signaling circuits



Dec. 5, 1933. G, CRlSsON 1,937,641

MULTIWAY CONNECTION FOR SIGNALING CIRCUITS Filed Sept. 3, 1931 O :5 Z j -(N-2)z 7m/at @ne A egatwe )Vgaa'vefmpedancf Impedance j Z3 I l Impedance INVENTOR BY wb/QC ATTORNEY Patented Dec. 5, 1933 i' MULTI-WAY.y CONNECTION Foa ciacorrs SIGNALING yGeorge Crisson, East Orange,v N.` J., assignor to American Telephone and Telegraph Company, a corporation o f New York Application september 3,1931. sriaiN. 561,076. ioclaims.' (c1. ris- 44) f This invention relates to a multi-way connection for signaling circuits,land more particularly 'to circuits in which a plurality of branches or sections lare connected together-in parallel or in series. -v l.

One robject of this'invention is to provide means Iby which the .echo or reflection eects which ordinarily occur-in such connections shall be eliminated. A further object is to provide means by which in such connections there shall be no transmission losses, and still a further Objectis a com-A bination of the two mentioned above in accordance with which neither reflectioneilects nor transmission lossesv shall occur in passing from any one ofthe group-of interconnected circuits into any other or others of the group. Two forms of connection will be dealt with in this invention, the onein which several circuits are connected in parallel and the one in which they are connected in series. v

' To carry out the objects of my invention, I make use cf negative resistances, of which rI have disclosed and described certain types in my Patent No. 1,776,310, September 23, 19304 and in an'article by me in The Bell System Technical Journal of July, 1931. By'proper choice of vthe type of negative impedance or resistance, and by y proper association with the lines to be connected,

, the impedance as seen looking from any one line A resistance; and Fig. 8 shows a or section into the remaining linesv is rendered the same as that of the 4one line, thus eliminating reflection losses. At the same time, in viewof the ability of the negative resistances to supply power, that -is their characteristic o'f being active rather than passive networks, the transmission `losses which wouldotherwis'e appear in connection with any one-circuit to which signals are being transmitted will be reduced, even to the zero point.

The invention will be better understood by reference to the following specication and vaccompanying drawing in which' Figure 1 shows the circuit for a plurality ofcircuits connected in parallel; Fig. 2 is for tliecase of circuits connected in series; Figs. 3 and 4 show schematic representations of two types of negative resistance; Figs. 5 and 6 show speciiic 'forms which the negative resistances cf Figs. 3 and 4 may take on; Fig. 7' shows still another form of negative modication of thecircuit of Fig. 1. y YReferring more specifically toV Fig. 1, there are shown a plurality of circuits A, B and C -which are to be joined inparallel such that signals originating in anyone line or section'will be sup- ;pliedto each-,andA all ofztheother sections For ed in parallel, it is evident thaton lookingffrom signals coming from any one of the sections.

simplicity we will at present assume that these lines are allidenticalin impedance, although'this restriction may be removed in manners hereinafter described. With the circuits thus connect'- I `the junction point'into the line A, from whichl signals may be assumed to emanate, there willV be seen an impedance Z, whereas upon looking in the other direction there is seen an impedance given by p N-1 Where N is the number of signaling circuits to be joined.r Thus, for signals coming from theline `A', therefwill be reflection losses at the junction and there will be at the Sametime large trans'- missionr loss so far as any one of the other circuits arejconcerned in Vview of the fact that they must share the power. f

.'Tooverccme this condition, I connect across,

1 theljunction line, as indicated in Fig. l, 'resistance impedance `which has a lnegative value, and for the particular circuitthisnegative resistance `is adjustedtoa value cf j ino echoes due to reflections at the junction for This is readily seen, for if there are N circuits` n vvall of equall impedanceA Z, then if one looks from the junction of circuit' A into the remaining circuits in parallel, theimpedance as seen is given signaling current owing from anyone circuit,

such as A, into each andA all of the other circuits Vis equallto the current in the originating branch.`

as explained in l'my patent cited 1 above, '.andto such anextentas toV just make 'up thevloss due to the bridged'connection so ltransmission takes l place frcm'any circuit intcjany cthe'r'circuit'With-Y H0 'wherefZ is the average impedance of the separate `working circuits;v A 'negative resistance'of this rvalueis just suiiicient to give a smooth line -termination;toeach 'of the sections, atf leastif they'are'lof'equal impedance ;v that is, there 'are 5 Furthermore, similar calculationsv show that the `supplied with current, itis evidentthat therevv s `This the negative resistance does inthe 'manner l Y understoodthat there Wouldbe vsome reflection rthe line impedance.

make it through transformers; asshown. I-Iere,'

again, there are no reflection losses if the negative resistance takes on a value of (N 2)Z, where Z is the average impedance of the working circuits. Thus, if one looks from the line A, whose impedance is Z, into the remainder o f the circuit, he sees an impedance given byV Also, the currentflowing in these lines taken in series is the saine as that inthe line A. Evidently, again; the E. M. Ffto yield this current has its source in the negative resistance.

vThe type of resistanceto be used is one of importance in order that the. circuits may be stable in operation'. Thus, in'fFig. 1 I make use of 'a negative resistance which I have designated as the shunt type, whereas in Fig. 2 I make use of the'series type. These types are shown diagrammatically in Figs. 3 and 4, and their respective characteristics have been set forth in detail in my patent cited above. One form "which these may take' on is' shown in- Figs. 5 and6, respectively; and it will be noted that they make use of vacuum tube ampliers with certain feed-back connections, whereupon their behavior is more properly described as negative resistances.

Still another form these negative `resistances may take on is shown in Fig. 'Z Which,i-it will be observed, simulates the connections of a'21-type repeater circuit. VIn this Fig. 'l the well'known hybrid co-il'is shown with a three-element ampliiier tube 9 and a network ladjusted to appropriate Value. pedance equal to thatseen looking out from the terminals at 11, thenp'ower Ywill be "supplied to both the network 10 and to the line coming in at 11, and the circuit behaves like a two-terminal element exhibiting the properties of a negative resistance. An important propertyof this circuit of Fig.' 7 is that by changing the poling of either kthe input coil or the outputcoil connected with the tube 9, the circuit' may be changed from a negative resistance showing shunt characteristics to one'showing series: characteristics, and' in applying this device tothe circuits of Figs. 1 or 2i t is necessary to use that connection which is' appropriate.

I have thus far implied that the negative resistances are pureresistances, and in many cases it would be siiiiicient to have themas pureresistances. In this case, of course, it vwould be at the junction if the lines orsections are not pure resistancesin themselves.. Ifthese reiiec-` tions become larger than desired, it would be Apossibleto introduce reactive elements such as Z of Fig; 2 with the negative resistances to secure a .more perfect simulation ofthe negative'oi For .this purpose any oi the mea-ns now well known in the art Yfor annuliing reactance may be used. I

In somecases where a plurality of lines or sections of the vkind described are arranged for If the network 10 vhas an'imparallel .or series connection, it occurs that at any one time only a limitednumber of the sections are to vbe connected. To provide for this greater iiexibility in the circuit set-up, while still retaining the balanced conditions described' 80 above, means may be provided 4such as switches Aor jacks so that the different circuits may be connected to the junction or disconnected, at will.

Such devicesshould be so arranged thatwhen any circuit is disconnected, a network having the 8% saineimpedance as' the circuit is substituted for any number of circuits less than N may be interconnected without disturbing the arrangement or adjustment of the apparatus at the'junction.

Y Numerous variations may be'made in my invention as I have thus far described it, and it is to 'be understood that these may be made without departing from the spirit of my invention. For example, in Fig. 1 it would be quite possible to connect the' lines A, Band C to the common junction point `through transformers, as shownin Fig.v 8. Such an arrangement would be highly advantageous in certain cases. For instance, if the lines A, B, C, etc. do not have the sameiOO impedance characteristic, they may be' brought to the same impedance as seen from the` junction point by using step-up or step-down transformers of appropriate ratio. Also, it will bejimder-- stood that instead ofusing transformers to"bring15 about this matching of impedances, it 'might be accomplishedy by any Vother type of network for such purpose now` Well known in the art. Also,

while the invention was described in terms of `at or near the average impedance of the N sections.

What is claimed is:

1. In a'multi-way circuit, a plurality of N work- .220 ing circuits'connected in circuit together and aV Y` negative impedance also connected in the circuit, tne latter being adjusted in magnitude to neutralize the impedances of N -2 of therworking circuits. g 'i125 2. In a multi-way circuit, ajplurality of N working circuits connected in series and a negative impedance also connected in series, the latter being adjusted in magnitude to the sum of the impedances of the working circuits minustwice theil() yaverage of the impedances of the circuits.

3. In a multi-way circuit, a plurality of N-Working circuits connected in parallel and a negative resistance associated therewith so that the impedance as seen looking from any one line is135 equal to the impedance of that' line.

4. In a multi-way circuit, a plurality of N work- -ing circuits connectedfin series and a negative impedance 'associated therewith so thatv the impedance as seen looking from anyone line'is equallz40 to the impedance of that line. j Y

5. In a"multiw ay circuit, a plurality .of-.N

working circuits associated`wth eachother .and

an active network associated Itherewithto neu-A tralize impedance to such anieitnt'that athere`45 are noV reiiection losses or transmissionlos'ses' for the' plurality of circuits. l

6. In amulti-way circuit, a plurality of N work'- ing. circuits. connected'in parallel at a" common.150

junction point and meansfa'ssociated therewithtoY neutralize impedance to such an extent that there are no reiiection losses or transmission losses at the junction of the plurality of circuits.

'7. In a multi-Way circuit, a plurality of N Working circuits connected in series and means as sociated therewith to neutralize/impedance to such an extent that there are no reflection losses or transmission losses for the plurality of circuits.

8. In a multi-way circuit, a plurality of N Working circuits of equal impedance 1 Z connected in parallel and a negative impedance of value I N-2 connected in parallel at the common junction.

9. In a multi-way circuit, a plurality of N Working circuits of equal impedance Z connected f in series and a negative impedance ofr value*V (N-2) Z connected in series therewith.

10. In a multi-Way circuit, a plurality of N Working circuits vof unequal impedance connected in parallel at a common junction point, a trans-r former ineach line prior to the connection and of such ratios as to bring all the lines to the same impedance Z and a negative impedance ofshunt characteristics connected in parallelat the junction point, saidresistance being adjusted to'a Value. Y

i. i N 2- y 90 l GEORGE CRISSON. 

